1. Field of the Invention
This invention relates to monitoring electro-magnetic radiation fields, and more particularly to dipole antennas for radiation monitors which have an extended frequency response both above and below the nominal flat frequency response for conventional dipole antennas.
2. Description of the Prior Art
The response of dipole antennas over a range of frequencies in electromagnetic radiation fields is typically achieved by the use of calibration factors to quantify the signal. On either side of the resonant frequency of the dipole antenna, a decrease in signal strength is experienced with both increasing and decreasing frequency in an otherwise uniform field. The very low impedance of antennas near the natural dipole resonant frequency is itself a factor which reduces the useful range of the antenna for broadband operation. While the use of calibration factors in the instrument can be effective in broadening the response over a widened frequency range, it requires a knowledge of the exact frequency of the signal. Also, when more than one signal is involved at the same time, it is difficult to determine the total energy in the field.
Accordingly, it is a primary object of the present invention to provide a dipole antenna structure for monitoring electromagnetic radiation fields over an extended frequency range characterized by an essentially flat frequency response without requiring the use of calibration factors to quantify the received signals and the need for knowing the exact frequency thereof.
It is a further object of the present invention to provide a dipole antenna structure for monitoring electromagnetic fields over an extended frequency range, characterized by an essentially flat response (i.e. constant sensitivity) thereover, which permit the determination of the total energy of an electromagnetic radiation field when more than one signal is involved.